Make markdown as an independent module

1 files changed, 369 insertions, 0 deletions

diff --git a/modules/markdown/markdown.go b/modules/markdown/markdown.go
new file mode 100644
index 0000000000..aad0553afe
--- /dev/null
+++ b/modules/markdown/markdown.go
@@ -0,0 +1,369 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package markdown
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"path"
+	"path/filepath"
+	"regexp"
+	"strings"
+
+	"github.com/Unknwon/com"
+	"github.com/microcosm-cc/bluemonday"
+	"github.com/russross/blackfriday"
+	"golang.org/x/net/html"
+
+	"github.com/gogits/gogs/modules/base"
+	"github.com/gogits/gogs/modules/setting"
+)
+
+var Sanitizer = bluemonday.UGCPolicy()
+
+// BuildSanitizer initializes sanitizer with allowed attributes based on settings.
+// This function should only be called once during entire application lifecycle.
+func BuildSanitizer() {
+	// Normal markdown-stuff
+	Sanitizer.AllowAttrs("class").Matching(regexp.MustCompile(`[\p{L}\p{N}\s\-_',:\[\]!\./\\\(\)&]*`)).OnElements("code")
+
+	// Checkboxes
+	Sanitizer.AllowAttrs("type").Matching(regexp.MustCompile(`^checkbox$`)).OnElements("input")
+	Sanitizer.AllowAttrs("checked", "disabled").OnElements("input")
+
+	// Custom URL-Schemes
+	Sanitizer.AllowURLSchemes(setting.Markdown.CustomURLSchemes...)
+}
+
+var validLinksPattern = regexp.MustCompile(`^[a-z][\w-]+://`)
+
+// isLink reports whether link fits valid format.
+func isLink(link []byte) bool {
+	return validLinksPattern.Match(link)
+}
+
+// IsMarkdownFile reports whether name looks like a Markdown file
+// based on its extension.
+func IsMarkdownFile(name string) bool {
+	name = strings.ToLower(name)
+	switch filepath.Ext(name) {
+	case ".md", ".markdown", ".mdown", ".mkd":
+		return true
+	}
+	return false
+}
+
+// IsReadmeFile reports whether name looks like a README file
+// based on its extension.
+func IsReadmeFile(name string) bool {
+	name = strings.ToLower(name)
+	if len(name) < 6 {
+		return false
+	} else if len(name) == 6 {
+		return name == "readme"
+	}
+	return name[:7] == "readme."
+}
+
+var (
+	// MentionPattern matches string that mentions someone, e.g. @Unknwon
+	MentionPattern = regexp.MustCompile(`(\s|^)@[0-9a-zA-Z_\.]+`)
+
+	// CommitPattern matches link to certain commit with or without trailing hash,
+	// e.g. https://try.gogs.io/gogs/gogs/commit/d8a994ef243349f321568f9e36d5c3f444b99cae#diff-2
+	CommitPattern = regexp.MustCompile(`(\s|^)https?.*commit/[0-9a-zA-Z]+(#+[0-9a-zA-Z-]*)?`)
+
+	// IssueFullPattern matches link to an issue with or without trailing hash,
+	// e.g. https://try.gogs.io/gogs/gogs/issues/4#issue-685
+	IssueFullPattern = regexp.MustCompile(`(\s|^)https?.*issues/[0-9]+(#+[0-9a-zA-Z-]*)?`)
+	// IssueIndexPattern matches string that references to an issue, e.g. #1287
+	IssueIndexPattern = regexp.MustCompile(`( |^|\()#[0-9]+\b`)
+
+	// Sha1CurrentPattern matches string that represents a commit SHA, e.g. d8a994ef243349f321568f9e36d5c3f444b99cae
+	Sha1CurrentPattern = regexp.MustCompile(`\b[0-9a-f]{40}\b`)
+)
+
+// Renderer is a extended version of underlying render object.
+type Renderer struct {
+	blackfriday.Renderer
+	urlPrefix string
+}
+
+// Link defines how formal links should be processed to produce corresponding HTML elements.
+func (r *Renderer) Link(out *bytes.Buffer, link []byte, title []byte, content []byte) {
+	if len(link) > 0 && !isLink(link) {
+		if link[0] != '#' {
+			link = []byte(path.Join(r.urlPrefix, string(link)))
+		}
+	}
+
+	r.Renderer.Link(out, link, title, content)
+}
+
+// AutoLink defines how auto-detected links should be processed to produce corresponding HTML elements.
+// Reference for kind: https://github.com/russross/blackfriday/blob/master/markdown.go#L69-L76
+func (r *Renderer) AutoLink(out *bytes.Buffer, link []byte, kind int) {
+	if kind != blackfriday.LINK_TYPE_NORMAL {
+		r.Renderer.AutoLink(out, link, kind)
+		return
+	}
+
+	// Since this method could only possibly serve one link at a time,
+	// we do not need to find all.
+	m := CommitPattern.Find(link)
+	if m != nil {
+		m = bytes.TrimSpace(m)
+		i := strings.Index(string(m), "commit/")
+		j := strings.Index(string(m), "#")
+		if j == -1 {
+			j = len(m)
+		}
+		out.WriteString(fmt.Sprintf(` <code><a href="%s">%s</a></code>`, m, base.ShortSha(string(m[i+7:j]))))
+		return
+	}
+
+	m = IssueFullPattern.Find(link)
+	if m != nil {
+		m = bytes.TrimSpace(m)
+		i := strings.Index(string(m), "issues/")
+		j := strings.Index(string(m), "#")
+		if j == -1 {
+			j = len(m)
+		}
+		out.WriteString(fmt.Sprintf(` <a href="%s">#%s</a>`, m, base.ShortSha(string(m[i+7:j]))))
+		return
+	}
+
+	r.Renderer.AutoLink(out, link, kind)
+}
+
+// ListItem defines how list items should be processed to produce corresponding HTML elements.
+func (options *Renderer) ListItem(out *bytes.Buffer, text []byte, flags int) {
+	// Detect procedures to draw checkboxes.
+	switch {
+	case bytes.HasPrefix(text, []byte("[ ] ")):
+		text = append([]byte(`<input type="checkbox" disabled="" />`), text[3:]...)
+	case bytes.HasPrefix(text, []byte("[x] ")):
+		text = append([]byte(`<input type="checkbox" disabled="" checked="" />`), text[3:]...)
+	}
+	options.Renderer.ListItem(out, text, flags)
+}
+
+// Note: this section is for purpose of increase performance and
+// reduce memory allocation at runtime since they are constant literals.
+var (
+	svgSuffix         = []byte(".svg")
+	svgSuffixWithMark = []byte(".svg?")
+	spaceBytes        = []byte(" ")
+	spaceEncodedBytes = []byte("%20")
+)
+
+// Image defines how images should be processed to produce corresponding HTML elements.
+func (r *Renderer) Image(out *bytes.Buffer, link []byte, title []byte, alt []byte) {
+	prefix := strings.Replace(r.urlPrefix, "/src/", "/raw/", 1)
+	if len(link) > 0 {
+		if isLink(link) {
+			// External link with .svg suffix usually means CI status.
+			// TODO: define a keyword to allow non-svg images render as external link.
+			if bytes.HasSuffix(link, svgSuffix) || bytes.Contains(link, svgSuffixWithMark) {
+				r.Renderer.Image(out, link, title, alt)
+				return
+			}
+		} else {
+			if link[0] != '/' {
+				prefix += "/"
+			}
+			link = bytes.Replace([]byte((prefix + string(link))), spaceBytes, spaceEncodedBytes, -1)
+			fmt.Println(333, string(link))
+		}
+	}
+
+	out.WriteString(`<a href="`)
+	out.Write(link)
+	out.WriteString(`">`)
+	r.Renderer.Image(out, link, title, alt)
+	out.WriteString("</a>")
+}
+
+// cutoutVerbosePrefix cutouts URL prefix including sub-path to
+// return a clean unified string of request URL path.
+func cutoutVerbosePrefix(prefix string) string {
+	count := 0
+	for i := 0; i < len(prefix); i++ {
+		if prefix[i] == '/' {
+			count++
+		}
+		if count >= 3+setting.AppSubUrlDepth {
+			return prefix[:i]
+		}
+	}
+	return prefix
+}
+
+// RenderIssueIndexPattern renders issue indexes to corresponding links.
+func RenderIssueIndexPattern(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
+	urlPrefix = cutoutVerbosePrefix(urlPrefix)
+	ms := IssueIndexPattern.FindAll(rawBytes, -1)
+	for _, m := range ms {
+		var space string
+		if m[0] != '#' {
+			space = string(m[0])
+			m = m[1:]
+		}
+		if metas == nil {
+			rawBytes = bytes.Replace(rawBytes, m, []byte(fmt.Sprintf(`%s<a href="%s/issues/%s">%s</a>`,
+				space, urlPrefix, m[1:], m)), 1)
+		} else {
+			// Support for external issue tracker
+			metas["index"] = string(m[1:])
+			rawBytes = bytes.Replace(rawBytes, m, []byte(fmt.Sprintf(`%s<a href="%s">%s</a>`,
+				space, com.Expand(metas["format"], metas), m)), 1)
+		}
+	}
+	return rawBytes
+}
+
+// RenderSha1CurrentPattern renders SHA1 strings to corresponding links that assumes in the same repository.
+func RenderSha1CurrentPattern(rawBytes []byte, urlPrefix string) []byte {
+	ms := Sha1CurrentPattern.FindAll(rawBytes, -1)
+	for _, m := range ms {
+		rawBytes = bytes.Replace(rawBytes, m, []byte(fmt.Sprintf(
+			`<a href="%s/commit/%s"><code>%s</code></a>`, urlPrefix, m, base.ShortSha(string(m)))), -1)
+	}
+	return rawBytes
+}
+
+// RenderSpecialLink renders mentions, indexes and SHA1 strings to corresponding links.
+func RenderSpecialLink(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
+	ms := MentionPattern.FindAll(rawBytes, -1)
+	for _, m := range ms {
+		m = bytes.TrimSpace(m)
+		rawBytes = bytes.Replace(rawBytes, m,
+			[]byte(fmt.Sprintf(`<a href="%s/%s">%s</a>`, setting.AppSubUrl, m[1:], m)), -1)
+	}
+
+	rawBytes = RenderIssueIndexPattern(rawBytes, urlPrefix, metas)
+	rawBytes = RenderSha1CurrentPattern(rawBytes, urlPrefix)
+	return rawBytes
+}
+
+// RenderRaw renders Markdown to HTML without handling special links.
+func RenderRaw(body []byte, urlPrefix string) []byte {
+	htmlFlags := 0
+	htmlFlags |= blackfriday.HTML_SKIP_STYLE
+	htmlFlags |= blackfriday.HTML_OMIT_CONTENTS
+	renderer := &Renderer{
+		Renderer:  blackfriday.HtmlRenderer(htmlFlags, "", ""),
+		urlPrefix: urlPrefix,
+	}
+
+	// set up the parser
+	extensions := 0
+	extensions |= blackfriday.EXTENSION_NO_INTRA_EMPHASIS
+	extensions |= blackfriday.EXTENSION_TABLES
+	extensions |= blackfriday.EXTENSION_FENCED_CODE
+	extensions |= blackfriday.EXTENSION_AUTOLINK
+	extensions |= blackfriday.EXTENSION_STRIKETHROUGH
+	extensions |= blackfriday.EXTENSION_SPACE_HEADERS
+	extensions |= blackfriday.EXTENSION_NO_EMPTY_LINE_BEFORE_BLOCK
+
+	if setting.Markdown.EnableHardLineBreak {
+		extensions |= blackfriday.EXTENSION_HARD_LINE_BREAK
+	}
+
+	body = blackfriday.Markdown(body, renderer, extensions)
+	return body
+}
+
+var (
+	leftAngleBracket  = []byte("</")
+	rightAngleBracket = []byte(">")
+)
+
+var noEndTags = []string{"img", "input", "br", "hr"}
+
+// PostProcess treats different types of HTML differently,
+// and only renders special links for plain text blocks.
+func PostProcess(rawHtml []byte, urlPrefix string, metas map[string]string) []byte {
+	startTags := make([]string, 0, 5)
+	var buf bytes.Buffer
+	tokenizer := html.NewTokenizer(bytes.NewReader(rawHtml))
+
+OUTER_LOOP:
+	for html.ErrorToken != tokenizer.Next() {
+		token := tokenizer.Token()
+		switch token.Type {
+		case html.TextToken:
+			buf.Write(RenderSpecialLink([]byte(token.String()), urlPrefix, metas))
+
+		case html.StartTagToken:
+			buf.WriteString(token.String())
+			tagName := token.Data
+			// If this is an excluded tag, we skip processing all output until a close tag is encountered.
+			if strings.EqualFold("a", tagName) || strings.EqualFold("code", tagName) || strings.EqualFold("pre", tagName) {
+				stackNum := 1
+				for html.ErrorToken != tokenizer.Next() {
+					token = tokenizer.Token()
+
+					// Copy the token to the output verbatim
+					buf.WriteString(token.String())
+
+					if token.Type == html.StartTagToken {
+						stackNum++
+					}
+
+					// If this is the close tag to the outer-most, we are done
+					if token.Type == html.EndTagToken {
+						stackNum--
+
+						if stackNum <= 0 && strings.EqualFold(tagName, token.Data) {
+							break
+						}
+					}
+				}
+				continue OUTER_LOOP
+			}
+
+			if !com.IsSliceContainsStr(noEndTags, token.Data) {
+				startTags = append(startTags, token.Data)
+			}
+
+		case html.EndTagToken:
+			if len(startTags) == 0 {
+				buf.WriteString(token.String())
+				break
+			}
+
+			buf.Write(leftAngleBracket)
+			buf.WriteString(startTags[len(startTags)-1])
+			buf.Write(rightAngleBracket)
+			startTags = startTags[:len(startTags)-1]
+		default:
+			buf.WriteString(token.String())
+		}
+	}
+
+	if io.EOF == tokenizer.Err() {
+		return buf.Bytes()
+	}
+
+	// If we are not at the end of the input, then some other parsing error has occurred,
+	// so return the input verbatim.
+	return rawHtml
+}
+
+// Render renders Markdown to HTML with special links.
+func Render(rawBytes []byte, urlPrefix string, metas map[string]string) []byte {
+	result := RenderRaw(rawBytes, urlPrefix)
+	result = PostProcess(result, urlPrefix, metas)
+	result = Sanitizer.SanitizeBytes(result)
+	return result
+}
+
+// RenderString renders Markdown to HTML with special links and returns string type.
+func RenderString(raw, urlPrefix string, metas map[string]string) string {
+	return string(Render([]byte(raw), urlPrefix, metas))
+}